CHROMOSOMAL LOCALIZATION OF THE MAJOR AND 5S RIBOSOMAL-RNA GENES IN THE EUROPEAN EEL (ANGUILLA-ANGUILLA)

The major (18S, 5.8S, and 28S) and 5S rRNA genes have been mapped by d ouble fluorescent in situ hybridization to European eel metaphase chro mosomes. The major rRNA genes were localized to a submetacentric pair of chromosomes that showed a consistent size polymorphism among the in dividuals studied. The 5S rRNA genes were clustered in a single locus that mapped to the centromeric region of an acrocentric pair. In contr ast to the major rRNA genes, no detectable polymorphism, in either siz e or intensity of the fluorescent signal, was observed. The chromosoma l organization of both families of rRNA genes are discussed in terms o f genomic organization and chromosomal evolution.